Pneumatic tire.



. Patented Nov. 25, |902. rga

TIRE.

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Ptented Nov. 25, |902.

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WILBRAHAM EDMUND, OE EALING, ENGLAND, ASSIGNOR TO HIMSELE,

AND ALISTER. MACNAB,

OE LONDON, ENGLAND.

PNEUMATIC TIRE.

SPECIFICATION forming part of Letters Patent No. 714,164, dated November 25, 1902,

Application tiled January 3, 1901. Serial No. 41,963. i110 model.)

' vented Improvements in or Relating to Pneumatic Tires, of which the following is a specication.

In the specifications of Dunns British Patents Nos. 14,173 and 15,952 of 1891 there is described a type of pneumatic tire in which the tread is rendered inflexible transversely, while, though it may be rendered inextensible in length it remains flexible and compressible longitudinally, whereby a broad iiat bearing -surface is constantly formed upon the body of compressed air Within the tire, while a narrow surface may be presented to the road, and whereby also, without impair-ing but rather improving the resilience of the tire by various devices which can advantageously be employed in a tire thus constructed, it is thoroughly protected against puncture.

Now the present invention relates to im-.

provements in pneumatic tires of the type referred to designedv to render such tires more efficient and reliable in use than heretofore.

Figure v1 is a cross-section showing a construction of tire according to this invention suitable for wheels of bicycles and other light vehicles. Fig. 2 is a cross-section, and Fig. 3 a part longitudinal section, showing a similar construction of tire suitable foruse With a motor-car, omnibus, or other heavy vehicle. Figs. 4 and 4fL are cross-sections showing modified constructions of tire. detail views showing constructions of treads suitable for use with tires of the kind illustrated in Figs. 2, 3, and 4. Fig. 14 is a detail view showing the mode of constructing the pockets of such tires. Fig. 15 shows a cross-section of an ordinary rim with means for adapting it for use with tires according to this invention.

To render a pneumatic tire of the kind referred to not only proof against failure by puncture, but also against failure through bursting or any other of the accidents to which pneumatic tires are commonly liable, there is provided according to this invention within the air-tube a, Figs. l, 2, and 3, of the Figs. 5 to 13a are to whatever degree of pressure is requisite to give the tire theweight supporting and resilient efficiency desired, after which the outer tube is infiated to practically the same pressure. By this means while the inner tube b remains fully disteuded and from the construction of the tire constantly bearing upon the inner surface of the transversely-inflexible tread c of the tire it is relieved of practically all strain, and its fabric is therefore not appreciably worn by the usage of the tire; but should the outer tube a wear out and burst or from any other cause become deated the inner tube b will maintain the tire without any material change of shape or loss of efficiency and without occasioning even a momentary stoppage of the bicycle or other vehicle to which the tire is attached until the outer tube can convenientlybe repaired.

In some cases two or more inner tubes h, such as described, may be used in accordance with this invention. Fig. 4 shows one such construction, in which three inner air-tubes b are used,.arranged side by side, whereof the intermediate oneis greatly dattened at its inv'ner and outer peripheries and the two side ones are shown circular in section, though of the outer tube a entirely fail, it is desir- 9o able to render the tread c in some Way inextensible longitudinally; but as this ineXtensibility need not be called into play so long as the outer tube a remains intact it need not be produced in such a way as would render it efficient throughout the life of the tire, but only in such a way that it would be efficient for temporary use when required.

In Fig. 1 the tread c is of india-rubber or equivalent material arranged between the outer air-tube a and the outer inextensible cover or pocket e of the tire, the said tread IOO being rendered inflexible transversly and puncture-proof by means of a bandf, of hard material, that is embedded in the tread c and which may be constructed in any suitable manner-as, for example, in any of the ways described in the said former specicationsso that while it is inflexible transversely it is flexible and compressible in the direction of its length. In Figs. 2, 3, and 4 the tread is arranged outside the cover or pocket.

For heavy road-vehicles the transverselyinflexible tread may advantageously be composed of a band of alternately arranged transverse plates or laminas g and h, (Figs. 5 to 13,) whereof those marked g are made of some hard material-such as wood, Celluloid, or metal (preferably steel or aluminium)- and those marked h are made of an elastic or yielding material-for example, india-ru bber. These plates or laminze (hereinafter called plates) may be united together and formed into a longitudinally-flexible and compressible band, which may at the same time be made endless and inextensible by bands or cords k, preferably of wire, passing through holes Z in the plates. When it is desired to make the laminated tread endless and permanently inextensible, it is preferably provided with three connecting-bands 7t,each consisting of a number of lengths or convolutions of Wire, the center band being made strong enough to sustain with a proper margin of safety the Whole longitudinal strain exerted by the air-pressure in the tire, and each of the other two bands being made of ratherV more than half this strength, the center band being preferably made rather tighter than the side bands, so that so long as it is effective the outer bands would be relieved of strain, and so retained in practically unimpaired strength to fulfil their function should the center band fail, which band could afterward be renewed when convenient.

The plates g and h may be threaded on the bands k, in which case each band may be composed of a numberoflengths of wire and have its ends adapted to be afterward coupled together, or the holes Z in the said plates may have openings fm, which should preferably open to the outer sides of the plates, as shown in Figs. 5 and 7. In this ease the plates g and h may be connected into a band by cementing them together, and after placing the band around the tread of the tire, as shown in Figs. 2 and 3, the wire connecting-bands k may be made up by winding a length of wire, coil upon coil, into the holes Z through the openings m. A lubricant and rust-preventing material, such as vaseline, not injurious to india-rubber, should rst be injected into the holes Z, so that the wires will become entirely embedded in it, and the openings 'm may be afterward suitably closed-as, for example, by string wound into them till they are filled up, the string being so treated, as

with rubber solution, that its strands will firmly adhere together, so that on its becoming worn its severed ends will not become loose.

In order to better utilize the elasticity of the plates h, of india-rubber, and to lighten the hard plates g, the latter are preferably formed with additional holes g', as shown in Figs. 2, 5, and 6. Sometimes the said band may be built up of groups of plates g and 71 the plates comprising each group being, as shown in Figs. 10, 11, and 12, threaded on pins n, which are driven tightly in the center plate g of the group, the other plates sliding upon the pins. These pins prevent the plates being tilted out of their proper upright radial attitude. When the holes l in the plates have openings m extending to the inner sides of the plates, the said openings should connect with the holes at the sides thereof, as shown in Fig. 13. In this case the plates may be slipped over endless connecting-bands la. The center band may be wound on and the others either made endless and the plates slipped over them or made up in the requisite lengths, the plates threaded on them, and the ends coupled.

The plates g h may be made of various shapes, sizes, and thicknesses, according to the purpose for which the tire to which they are to be applied is intended. It is preferred to make them straight on both sides, nearly as long as the breadth of the tire, and, except in the case of very wide tires, about a third of their length in breadth and with their ends beveled, so that their outer sides should be of about half the length of their inner sides, or they maybe made ofaplano-convex shape, as shown in Fig. 4a.

Fig. 13a shows a further modified construction of tread suitable for light vehicles. In this example the cross-sectional shape of the tread is similar to those shown in Figs. 2 and 5 to 13; but it is composed of alternate concentric layers g' and h', of canvas and indiarubber, cemented together. Such a tire may be rendered inextensible longitudinally by circumferential bands embedded therein or by substituting for one of the layers of canvas a layer 7a', of strong circumferential threads. In this case means, such as a plate f, must be provided for rendering the tread transversely inflexible. In this way treads suitable for heavy vehicles can be easily and cheaply constructed that are not only transversely inflexible and longitudinally flexible, compressible, and inextensible, but are also incompressible sidewise, so that the loss of power which is involved when an elastic body, such as the india-,rubber commonly used for tire-covers, is pressed under great weight between a tire and the ground is avoided. These treads are also much more durable than ordinary rubber covers.

It has been found important to secure to the inner side of the tread and adjacent to the edges thereof` approximately wedgeshaped strips p, Figs. 1, 2, 4, and 4a, of rubber, to distribute the transverse flection of the IOO IIO

tire down its sides and prevent risk of the edges of the laminated Itread cutting the fabric.

A band composed of plates g h, arranged as described, may be placed inside the tread of a tire, as shown in Fig. 4, in which case it need not be rendered inextensible in length, except for temporary use, as hereinbefore described. Preferably, however, the band is made permanently inextensible in length, as hereinbefore described, and put on over the tire when it is deflated. Then on ination the'inextensibility of the band holds it in place and also makes the tire secure on the wheel, so that the tire need not be provided with any of the usual attachment devices.

To produce tires according to this invention of the maximum strength and durability at the minimum cost and so that the cost of their maintenance shall also be the minimum practicable, they may advantageously be made as follows: To form the inner tube b, Figs. 1 to 4, an air-tube b, Fig. 14, of good quality india-rubber and of suitable size is drawn on toastraight round mandrel q,which it approximately fits and which may be col-4 lapsible, and around the tube is placed alayer 1', of light but good quality cotton or other suitable textile fabric, which is cut at an angle of forty-five degrees and is previously covered on its outside with india-rubber solution. A layer t or two or more layers of very strong thread is or are by suitable appliances then wound in a close spiral all over the outer surface of the fabric, the thread being passed through rubber solution in the process. so that it will be covered with a film of rubber that will cause the adjacent convolutions of thread to firmly adhere to one another and to the outer surface of the fabric r. When the solution is thoroughly dry, the inextensible tube or pocket thus produced is freely powdered withmateriahsuch as French chalk. The combined pocket and air-tube is then removed from the mandrel and drawn inside another compound tube made in the same way, but slightly larger than the first one. The ends of each of the two air-tubes are then joined together, and the joints between the ends of the ineXtensible pockets are covered by movable sleeves of similar material previously passed onto or into the tubes. The external surface of the outer compound tube or so much of1 it as requires protection is then covered with a thin layer of india-rubber, preferably having a backing of light looselywoven cotton cut at an angle of forty-five de grees. The combined inner and outer compound tubes thus constructed may then be placed around a wheel-rim, the laminated tread hereinbefore described placed around them, and it may be made to adhere to the outer periphery thereof. The inextensible wire bands k may then be wound in place in the tread and first the inner tube b and then the outer tube ainflated, as he'reinbefore described. Tires thus made will iit any ordinary wheel-rims; but it is preferred to use them on flat rims u', Figs. 2, 3, and 4, of greater breadth than the tires at their broadest part, so that the sides of the tires when they are compressed by a great weight instead of overhanging the rims and being liable to be cut on their edges may flatten out on the sides of the rims, and thus gain increased bearing power the more the tires are compressed and so that the outer edges of the wheel-rims may protect the tires from abrasion on curbs and the like. The rims should preferably have rounded edges, and they may have a central shallow channel with well-rounded edges to assist in Aplacing and keeping the tires laterally true, or the tires may be placed laterally true by means of studs s, Fig. 2, secured in their base and entering holes provided for them in the rims. The surface of the rims may be quite flat, and the central channel maybe formed on them by securing around them at the sides metal bands fu, Fig. 2, each of which might be surrounded by strips of rubber. When it is desired toapply the tires to Wheels having concave rims, instead of placing them directly in the rims it is preferred to first secure around each rim a dat metal tire which may be formed of a metal band w, Fig. 15, having a central shallow channel .fr of such breadth that its under side will fit the mouth of the wheel-rim y and lateral beads z to stiften and nish it.

Though generally unnecessary, it is preferred, particularly in the case of heavy vehicles, to provide for the better securing of the tire on the rim a metal band 1, Figs. 2 and 4, inclosed in a suitable sheath 2 and placed in the base of the outer pocket e or, it may be, of the inner pocket. This band may be IOO constructed in any well-understood manner,

and when the tire has an inextensibletread, as described, it generally requires no fastening. Should it, however, be desired to attach the tire in the most secure manner, two metal bands 1 and 3 may be used, as described in the specification of an earlier British patent, No. 1,067 of 1896, placed one over the other in the base of the tire, as shown in Figs. 2 and 3, with their ends at diametrically opposite sides of the wheel, short strips of metal, through which the valves 4 and 5 pass, being provided to overlap their ends and ill the gap between them. The said bands 1 and 3 after they have been pressed tightly in place are secured by means of the two air-valves4 and 5,'of which 5, belonging to the inner tube, is passed through a hole 7 iu the center of the outer band 1. The band l may be placed within the pocket of the outer tube ct and the band 8 within the pocket of the inner tube b, the latterband being preferably slightly narrower than the'former and being secured against displacement circumferentially in any convenient manner, as by cementing its central portion within its' sheath.

One advantageof makingthe pockets in IIO' the manner described is that when the pocket e of the outer tube begins to show signs of wear it can be readily placed in a new posision by turning it partly around its longitudinal axis, so that a different part may be brought next the Wheel-rim and that fresh parts may be brought into the position subject to the severest wear, the position of the tread being ofcourse shifted at the same time; also, the pockets will lie nearly equally well in almost any position, and their position can be changed several t mes before they are quite Worn out. Should it be desired to turn the pocket around till an edge of the outside rubber cover would be exposed, the outer rubber cover may easily be stripped off the outer pocket and be replaced in a new position. When the position of the pocket e is thus changed transversely, the rubber air-tube a may be kept in its original position (to avoid having to shift the position in it of the valve) by turning it around, as may be necessary, inside the said pocket. The valves maybe arranged to protrude between the ends of the pockets and through holes in the sleeves r', covering their ends, the sleeves 1" being kept in the same position relatively to the air-tubes. The Valve of the inner tube when placed diametrically opposite the other valve must either pass through a hole in the outer pocket or that pocket may be divided Where this valve passes through it and the joint covered by another sleeve through a hole in which the valve may be passed. By periodically changing the position of the pocket c the life of the tires may be increased at least fourfold, while in vehicle-tires so little liable to injury or failure as these are and designed never to require immediate repair it is unnecessary to provide such facilities for repair as is desirable With other constructions, particularly in cycle-tires. Furthermore, the tires may be made of such breadth that Whatever the load to be carried they will support it with the desired degree of resiliency without requiring to be inflated to a higher pressure than fortyive or sixty pounds-that is, three or fouratmospheres. At such a pressure the tires are not liable to heat in use, as they do at higher pressures, Which heating is found to be very destructive to the tires; also, this pressure can be maintained by thin layers of suitable thread, which is employed to the best advantage (as regards resisting the strains it has to bear) When Wound in a close spiral, as hereinbefore described, and the thin fabrics which can then be used wear very much better than the thicker ones necessary to withstand the high pressures required in tires of ordinary construction on heavy vehicles, such thick fabrics rapidly perishing from the effect of the internal friction set up by their flection. Besides many other advantages of considerable importance, it is regarded in this connection as an advantage of the highest possible importance that by the construction described and for reasons which need not be here described in detail transv'ersely-inlexid ble treads, such as described, enable a tire of given size to support a given load with about forty per cent. less air-pressure than a tire of corresponding size of ordinary construction. This is a point of so much importance that it is believed to be essential to the construction of pneumatic tires designed to be successfully used on heavy Vehicles to take advantage of it.

By the construction described tires can be made of various sh`apes; but it is preferred to make them so that they have an approximately square or flat section, with the outside corners beveled off so as to narrow the bearing-surface on the road. It is also preferred, except in very broad tires, to make the laminated tread of a thickness equal to about one-third of the depth of the complete tire, so that the depth and breadth of the internal air-space are to one another about as two is to three or of greater width in proportion to depth.

To repair the tires, which from their construction should be very rarely necessary, and should never be necessary till a journey is finished, they should be dedated and removed from the rim. The outer rubber cover, with its backing of cotton, may then be stripped olf the damaged part, and if it is a burst requiring a large patch on the air-tube the outer pocket e may be cut transversely all around, Which only involves cutting the inner skin and the wound thread t at one place, when the parted ends of the pocket can be drawn aside to expose the air-tube a as far as necessary. The air-tube may then be patched in the usual Way, the parted ends of the pocket brought together again, and a strip of solutioned material bound over them. lf the pocket has burst badly, it may require binding up, which should be done with solutioned tape of isolated threads corresponding with the material of the pockets. The outer cover should then be stuck down again, and in applying the tire to the Wheelrim it is desirable to place it in a slightlydilferent position from its former one and to correspondingly shift the position of the tread. Should the inner tube b be damaged, which it is believed should be a very rare occurrence, the outer air-tube should be opened at the joint, the outer cover being divided there, if necessary, and the inner tube pulled circumferentially around till its damaged part is exposed. The inner pocket may then be divided transversely and the repair eected as above described with reference to the outer tube. Should there be difculty in discovering a damaged part in the inner tube, both air-tubes may be unjoined and the inner one Withdrawn for testing and repair. When a renewal is necessary, it should only, except at long intervals, be of the outer pocket,which from its construction would cost only a very small part of the cost of a new cover of an ordinary tire.

All the parts of the tires are designed to IOC IIO

wear much better than do the tires of ordinary construction as hitherto used on vehicles, both because of their special construction and because the tires require much lower air-pressures than have hitherto been necessary in vehicle-tires. Furthermore, tires constructed as described, particularly when used on heavy vehicles, will be not only cheaper to produce, more durable in use, and much cheaper-.and less troublesome to maintain in efcient condition than tires as still commonly constructed, but they will also be more easy running and resilient.

It will be seen that constructed as described tires according to this invention can readily be made without'costly special appliances to it rims of all shapes and sizes and to carry vehicles of any weight.

As will be well understood, transversely-inflexible treads and inner air-tubes, such as herein described, can be employed in conjunction with tires of various ordinary constructions, and the constructions herein described may be variously modified and variously combined hier se or with other constructions of tires.

The outer pocket may be made to open like the cover of an ordinary detachable tire. To do this, it should bc made on a larger mandrel than otherwise, cut open when wound, and sheaths formed in or on the edges in any approved manner. Bands should then be provided in these sheaths, as in some of the constructions shown in the before mentioned prior specification, No. 1,067 ofl896.

The interior of the inner air-tube b may be lined with a viscous substance adapted to check osmosis and porosity.

I am aware that pneumatic tires have heretofore been constructed with two or more tubes, either air-retaining and inextensible,

or only air-retaining, and placed side by side, one on the top of the other, one within another, and otherwise, and Ibelieve patents describing all these arrangements are now void. So far, however, as I am aware in every case the arrangement has been such that failure of one air-tube if it did not involve the entire deflation of the tire involvedr at least such a material diminution in its efficiency as to necessitate a stoppage to wholly or partly reinate it, and in no case has a construction been devised, such as that hereinbefore described, in which owing to the dattening of the interior surface of the tread the inner tubel will on failure of the outer tube effectively maintain the eiiiciency of the tire without any material change of shape,

so that the tire being practically unpunctur able, as stated, no interruption of the progress of the vehicle to which it is aflixed need be involved by any probable failure of the tire. I am also aware that laminated tires have heretofore been constructed; also, that laminated bands or treads have been used in con- .junction with pneumatic tires, the laminae being either of leather, leather and rubber, or rubber and metal; but, so far as I am aware, composite laminated bands, such as hereinbefore described, have not heretofore been used in connection with pneumatic tires so designed as to secure the objects attained by the present construction.

What I claim is- 1. In a pneumatic tire, the combination of a transversely-inexible and longitudinally flexible and com pressible tread having a wide practically flat inner periphery and separately-inflatable air-tubes each made of airretaining and laterally-inox tensible material, arranged one inside the other, and adapted to take a flat bearing against the flat inner periphery of said tread, substantially as described for the purpose set forth.

2. In a pneumatic tire, the combination of a transversely-iniiexible and longitudinally flexible and compressihle tread having a wide practically flat inner periphery, flexible means extending through and adapted to render said tread longitudinally inextensible, and separately-intlatable air-tubes each made of. airretaining and laterally-inextensible material, arranged one inside the other, and adapted to take a flat bearing against the flat inner periphery of said tread, substantially as described for the purpose set forth.

In a pneumatic tire, the combination of a transversely-indexible and longitudinally flexible and compressible thickened tread having a practically flat outer periphery and a wider practically dat inner periphery, and separately-inflatable air-tubes each made of air-retaining and laterally-inextensible material, arranged one inside the other, and adapted to take a wide practically flat bearing against the wide inner periphery of said tread, substantially as described for the purpose specified.

4. In a pneumatic tire, the combination of a transversely-infiexble and longitudinally iiexible and com pressible tread having a wide practically fiat inner periphery, separatelyinflatable air-tubes each made of air-retaining and laterally-inextensible material, arranged one inside the other, and arranged to take a wide practically dat bearing against the inner periphery of said tread, said air-tubes being each charged with air under practically the same pressure, substantially as described for the purpose specified.

5. The combination with a wheel having a wide practically flat outer peripheral portion, of a pneumatic tire comprising a transverselyiniiexible and longitudinally flexible and compressible tread having a wide practically at inner periphery and two separately-inflatable air-tubes arranged one inside the other, said air-tubes being each made of air-retaining and laterally-inextensible material and of such peripheral length and cross-section that when inflated they will take a wide practically flat bearing against the outer periphery of said IOO IIO

Wheel and against the inner periphery of said tread, substantially as described.

6. The combination with a Wheel `having a wide practically iat outer peripheral portion, of a pneumatic tire comprisinga transverselyiniiexible and longitudinally flexible compressible and inextensible tread having a Wide practically lat inner periphery and two separately-intlatable air-tubes arranged one inside the other and between the wheel rim and tread and each composed of an india-rubber tube inclosed within an outer pocket comprising one or more layers of thread Wound in a close spiral, said air-tubes being made of such peripheral length and cross-section that when inflated they will take a Wide practically ilat bearing against each other and against said Wheel rim and tread and leave air-spaces between them at the sides, and approximately wedge-shaped annular filling-strips arranged between the edge portions of the tread and the adjacent portions of the outer air-tube, substantially as described for the purposes specified.

7. In a pneumatic tire, the combination with an iniiatable air-tube having an airvalve by which it can be charged with air under pressure, of a transversely-inflexible and longitudinally flexible and compressible tread l having one or more practically inextensible bands extendinglongitudinally therethrough.

8. In a pneumatic tire, the combination with an inflatable air-tube having an air- Valve by which it can be charged With air under pressure, of a laminated transversely-iniiexible and longitudinally Iiexible and compressible tread having a practically inextensible band or layer extending longitudinally therethrough.

9. In a pneumatic tire, a transversely-inexible and longitudinally flexible and compressible tread having inextensible bands extending longitudinally therethrough, one or some of said bands being made tighter than the other or others, substantially as described for the purpose speciied.

10. In a pneumatic tire the combination with an air-tube having an air-valve, of a laminated tread composed of transversely-arranged perforated plates of hard and soft material placed side by side, and inextensible bands extending through the holes in said plates.

11. In a pneumatic tire, a laminated tread composed of transversely-arranged hard and soft uniformly-perforated plates arranged side by side and having passages extending from the holes therein to one side of the tread, and inextensible bands that are inserted through said passages and rest in said holes, substantially as described.

12. In a pneumatic tire, a laminated tread composed of transversely-arranged hard and soft plates placed side by side and formed with juxtaposed holes from one at least of which a passage extends to the exterior of the tread, and inextensible bands composed of coils of Wire extending through the juxtaposed holes, substantially as described.

13. In a pneumatic tire, alaminated tread composed of transversely-arranged plates of alternately hard and soft material, the plates being formed With juxtaposed holes and the plates of hard material being formed With additional holes, and inextensible bands extending through said juxtaposed holes, substantially as described.

14. In a pneumatic tire, the combination of a laminated transversely-inflexible and longitudinally flexible and compressible tread having a Wide or laterally-extended inner periphery and separately-infiatable air-retaining and inextensible tubes arranged one inside the other and adapted to take a wide bearing against the wide inner periphery of said tread, substantially as described.

15. In apneumatic tire, the combination of a laminated transversely-iniexible and longitudinally flexible compressible and inextensible tread having a Wide or laterally-extended inner periphery and separately-inlatable air-retaining and inextensible tubes arranged one inside the other and adapted to take a Wide bearing against the wide inner periphery of said tread, substantially as described.

16. A pneumatic tire comprising a trans- Versely-intlexible and longitudinally flexible and compressible tread having a Wide inner periphery and composed ot transversely-arranged plates of alternately hard and soft material, and inextensible bands extending longitudinally therethrough, an inner air-retainingand inextensible tube adapted to take a broad bearing against the inner periphery of said tread, and an outer separately-inflatable shield or protector that normally relieves the inner tube of strain.

17. A pneumatic tire comprising separatelyinliatable ai r-retaining and inextensible tubes arranged one inside the other, and alaminated laterally-infiexible and longitudinally iiexible and compressible tread having a Wide or laterally-extended inner periphery arranged outside of and against which said tubes bear with a attened surface, substantially as described.

18. 'Ihe combination with a wheel having a flat outer periphery, of a pneumatic tire comprising a transversely-inflexible and longitudinally flexible and compressible tread having a Wide inner periphery, and separately-iniiatable inner and outer air-retaining and inextensible tubes arranged between the wheel rim and tread and adapted to take la flat bearing against each of them, substantially as described.

19. The combination with a Wheel having a iat outer periphery, of a pneumatic tire comprising a transversely-inflexible and longitudinally tlexible compressible and inextensible tread having a wide inner periphery, and separately-inflatable inner and outer air-retaining and inextensible tubes arranged be- IIO tween the wheel rim and tread and adapted to take a flat bearing against each of them, substantially as described.

20. The combination with a Wheel having a Iiat outer periphery, of a pneumatic tire Comprising an Aexternal laminated tread having a flat inner and outer periphery and composed of transversely-arranged plates of al- Iernately hard and soft material and inextensible bands extending through said plates and two separately-inflatable air-retaining and inextensible tubes arranged one inside the other and within said tread and adapted to take a flat or extended bearing,T against the same, substantially as described. 

